1. Introduction
Assuring the highest level of safety is significant from an economic and strategic view. This applies to both historical and new reinforced structures against dynamic loading, for example, earthquakes. This can be accomplished if the dynamic characteristics of the buildings such as natural frequencies and mode shapes are firmly determined. Modal analysis is a technique that evaluates the modal parameters of a structure. These parameters are key to the determination of the finite element model updating, structural control, damage detection, and long-term structural health monitoring.
The evaluation of the dynamic characteristics using ambient vibration measurements is a tough task due to the presence of noise having dominant frequencies that could be involved in the modes of vibration, especially when the position and orientation of the sensors are not well placed. This noise effect could be resolved by conducting various tests and putting the sensors in the optimum setting. After that, the results obtained from the measurements can be considered almost accurate [
1]. The application of well-known different identification techniques include: The Crystal-Clear Stochastic Subspace Identification (CC-SSI) method [
2], the Stochastic Subspace Identification (SSI) method [
3], and the Enhanced Frequency Domain Decomposition (EFDD) method [
4]. The use of the ambient vibration measurements has been proven to be relatively fast, cost reducing and economically efficient for the determination of dynamic characteristics [
5].
The experimental measurements taken during different stages of construction provide more information for the structure compared to the ones obtained from only a single measurement at the completion stage of building. There have been a few similar studies conducted in the past [
6].
Rombach [
7] concluded that one of the most important advantages of construction-stage analysis is that the engineer can examine stress distributions as well as deformations at different levels of the construction sequence. Arslan and Duemuş [
8] and Kaplan et al. [
9] determined natural frequencies, mode shapes and damping ratios of full-scale one-storey one-bay infilled RC frames for bare frame, brick infilled and brick infilled with plaster using the Operational Modal Analyses method under ambient vibration. Results demonstrated that the dynamic characteristics change fundamentally relying upon the existence of an infill wall and plaster, and should be considered in structural analysis. Experimental and analytical approaches have been noted in many masonry-infilled RC buildings researchers such as the evaluation of dynamic characteristics (natural frequency in particular). Bayraktar et al. [
10] found that the first measured natural frequencies of three buildings which consisted of three construction stages named bare frames, infill walls, and completed building stages, were greater than the calculated frequencies. Al-Nimry et al. [
11] investigated the impact of cracking of the six-storey building in the period of vibration. Bikçe et al. [
12] showed that the period obtained from the analytical results increased half a percent with both the measured and code values. Amanat and Hoque [
13] used modal analysis to determine the fundamental frequency of vibration of several forms of RC-framed buildings infills and concluded that the primary parameters affecting the period are the height, the number, length of bays, and the amount of infills. Also, they observed that the infills’ presence increased the frequencies by about 30%. Practically, most of the earthquake regulations neglect the effects of the infilled plaster work and design process [
14].
The finite element method is a useful tool for engineers to assess, clarify and comprehend the conduct of any structural system. Finite element method (FEM) is a numerical solution method which looks for an approximate solution for various engineering problems. Timurağaoğlu et al. [
15] studied the behavior of reinforced concrete frames with brick and gas concrete infill walls using analytical and finite element methods. The one-storey reinforced concrete frame system, which has been experimentally studied before, was modeled with the help of the computer program. The results obtained from the analysis were compared with the experimental ones and the effects of the infill wall to the frame behavior were examined. In addition, the different equivalent compression bar models available in the literature were modeled in the computer environment with the help of finite element method, and the analysis results were compared with those obtained from experiments. Kubalski et al. [
16] adopted numerical models in order to describe the inelastic behavior of the system, as demonstrated by the acquired results of the overall structural response as well as the damage propagation within the infill wall. Comparing between experimental and numerical techniques underlined the valuable contribution of validated numerical simulations to infer rational recommendations for the design of masonry infilled frames. Khatiwada and Jiang [
17] demonstrated in the study the development of a finite element model of the infilled frame with the masonry wall under monotonic lateral loading. The force-displacement curve, failure mode and crack pattern demonstrate that the model is able to simulate the behavior of an infilled frame. The study also shows that the simplified micro modeling technique with cohesive surface is relevant in reproducing extensive outcomes. Furtado et al. [
18] studied the impact of the infill masonry walls’ presence in the seismic performance of a 15-storey high-rise building situated in Nepal. They utilized the obtained results to calibrate the numerical model built in the software SAP2000 [
19]. The researchers carried out linear elastic analyses to evaluate the effect of the infill panels in the expected dynamic response of the structure. The panels’ presence increased the storey shear and the maximum base shear by about 20%. It also increased the torsion effect. In recent years, the effects of plaster work on the seismic behavior of infilled frames have been investigated by several researchers. Plastering significantly affects the behavior of infill walls and also increases the natural frequency, stiffness and strength of the structures [
20,
21,
22].
The numerical modeling necessary to determine the building’s dynamic properties is similar to the model used to predict ‘static’ behavior or to evaluate safety under given loads; therefore, the results go beyond assessing dynamic behavior. This study aims to:
Provide information about the dynamic characteristics of the Turkish RC masonry buildings at different construction stages.
Determine the modeling errors through comparison study results found in the laboratory.
Understand the effect of the structural component and material such as wall and plaster work on dynamic characteristics of the completed building.
Compare the ultimate displacements and principal stresses for each stage.
In this study, numerical modeling has been conducted by using ABAQUS software at each stage. The finite element model is described, and the main calculated results are presented. The measurements and calculations are then compared to provide a better understanding of the building behavior and to identify where the numerical model needs to be improved.
Novelty of This Study Paper
The main contribution of this paper is to investigate both analyses (modal and static) of the reinforced concrete (RC) frame building during different construction stages, taking into consideration the effect on the modeling masonry infill (MI) and plastering brick walls, as well as a comparison between experimental and analytical results of the fundamental frequencies is performed. An analytical model analysis is performed on the three-dimensional finite element model developed using the ABAQUS software package.